1. Field of the Invention
The present invention relates to a hand-held transducer probe of a medical Doppler device. More specifically, the present invention relates to a probe which has mechanism for visually indicating the relative direction of internal body matter reflecting ultrasound waves transmitted from the probe. Such mechanism indicates whether the reflecting matter is moving toward or away from the probe.
2. Prior Art
In a continuous wave medical Doppler ultrasound device, a transmitting transducer beams ultrasound waves of a known frequency into the body. A receiving transducer is positioned closely adjacent to the transmitting transducer. For example, both the transmitting transducer and receiving transducer can be incorporated in a slender "probe" connected to the remainder of the medical Doppler ultrasound device by an electrical cable. The receiving transducer detects waves reflected from internal body matter such as blood. In accordance with the well-known Doppler effect, the difference in frequency of a wave before and after reflection indicates the velocity of the reflecting matter relative to the wave transmitter.
In pulsed medical Doppler devices, a single transducer can be used to transmit bursts of ultrasound waves spaced in time and, between transmissions, the same transducer is used to detect reflected waves.
Conventional medical Doppler devices generate electrical signals based on the frequency difference between transmitted and reflected waves. Such signals often are in the audible frequency range. Consequently, one convenient output is simply an audible output having a frequency content identical to the frequency content of the electrical signal. The electrical signal can be amplified and used to drive speakers or headphones. When a probe is pointed at an angle toward an artery, the audible output sounds like pulsed swishing of blood through the artery caused by beating of the heart.
Known devices provide various other types of outputs such as chart records of amplitude and/or frequency content or real time frequency spectrum graphs on a video display.
A single electrical signal corresponding to the frequency difference between transmitted and reflected waves provides an accurate indication of relative speed when the angle of transmitted and reflected waves relative to the direction of movement of the reflecting internal body matter is known. A single signal does not provide an indication of the relative direction, i.e., whether the reflecting matter is moving toward or away from the probe. It is known, however, that direction can be detected by providing quadrature outputs which are outputs that are identical but differ in phase by 90 degrees. Either signal provides velocity information and direction is indicated by which of the two outputs is leading in phase.
In a blood flowmeter, speed may be indicated by the frequency of an audible output and/or a visual display on the master control unit, volume of blood flow may be indicated by audible volume and/or visual information on the master unit, and direction may be indicated by stereo headphone or speaker channels and/or by visual indicators on the master unit. It may be difficult for a user to keep track of the desired information while at the same time manipulating the probe and then maintaining it at a desired location and angle.